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Ghrelin Effects on Appetite

Researchers found that the hormone ghrelin increases activity in the pleasure centers of the brain when food is sensed. Even when just looking at pictures of food, brain imaging shows that people receiving an infusion of ghrelin have stronger reactions in the pleasure centers of the brain. In a similar study, both lean and obese people who were administered ghrelin ate significantly more calories at an open buffet than those who received a placebo.

Ghrelin has been shown to encourage people to eat through its effects on the hypothalamus as well as other parts of the brain. There are both metabolic and pleasure signaling involved. Ghrelin does not just affect one part of the brain, but activates an entire network -- food is actually seen more acutely, and remembered better when ghrelin is high.

The reward centers of the brain activated by ghrelin are the same as those involved in drug addiction. One of the researchers, Alain Dagher of the Montreal Neurological Institute at McGill University said:

That shows it's reasonable to think of high-calorie food as having addictive potential.

Citation:
Publishing in Cell Metabolism 7, 400--409, May 2008. Ghrelin Modulates Brain Activity in Areas that Control Appetitive Behavior. By Saima Malik; Francis McGlone; Diane Bedrossian and Alain Dagher.